In article , Fishter writes
I think that getting the wires the right length is the key. Trying to fold up any extra wire is a no-no. Hold up the switch plate and work out exactly where all the wires are going, then cut them so there is just enough for you to get in and tighten the screws. You should only need the switch plate 20mm (or less) away from the wall to put the wires in and tighten the screws.
Also having the right depth of backbox helps, you get extra deep backboxes for cooker switches.
(eventually managed mine at the 3rd attempt)